I recently upgraded my Shimano 7speed (13-23) setup to 9 speed (12-23). I purchased the 9 speed upgrade with a new wheelset, but retained my older Shimano FD-6401 front deraileur. I have been unable to adjust the front deraileur to eliminate throwing the chain off occasionally when shifting from the large chainring (53T) to my small chainring (39T). I decided to replace the front deraileur with the new FD-6500 which is easier to adjust, but occassionally it will still drop the chain. It is more prevalent when shifting from the 53X21 or 23 down to the 39T chainring. Should I avoid shifting when the chain is crossed over that far??

I am still using the 6400 series crank arms with the 9 speed chainrings and 9 speed chain...any thougths???